Monhegan Light is easily seen at night from locations on the mainland. On some occasions it is possible from viewing this light at night to determine someone has been in the lantern room. So how is this possible from many miles distant? The answer may be found by comparing these two Monhegan Light photos.

It is difficult to tell from the Jeremy photo but these are not window shades. These shades are intended to be in the lowered position at night when the lamp is lit. They used with the newer rotating lamps that produce a high intensity flash characteristic.

These curtains are suspended from the ceiling, the inside roof of the lantern. When lowered they extend down to fill the space between the lamp and the windows in an arrangement similar to the spokes of a wagon wheel extending out from the hub. If you look at the roof of the lantern in the Ross photo you can faintly see four curtains rolled up forming a black X on the roof above the lamp. If someone has been in the lantern and raised the curtains it is possible to tell from the light at night that the curtains were left in the raised position. Can you guess the purpose of these curtains?

Fred. You are correct. These these are anti-reflection curtains. They prevent a false flash from light reflected from the lantern glass. The new lamps have a very compact beam and this reflection can be nearly as bright as the direct light from the lamp thus a single flash light would show a double flash. These curtains are raised to allow full access to the lantern area and often have been left in the raised position thus one can tell from the extra flash at night that someone has been in the lantern.